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International Journal of Navigation and Observation
Volume 2008 (2008), Article ID 175468, 7 pages
Research Article

GPS Time and Frequency Transfer: PPP and Phase-Only Analysis

1Royal Observatory of Belgium, 1180 Brussels, Belgium
2Instituto Nazionale di Ricerca Metrologica, 10135 Torino, Italy

Received 31 August 2007; Revised 15 February 2008; Accepted 8 May 2008

Academic Editor: Patrizia Tavella

Copyright © 2008 Pascale Defraigne et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


To compute precise point positioning (PPP) and precise time transfer using GPS code and phase measurements, a new software named Atomium was developed by the Royal Observatory of Belgium. Atomium was also adapted to perform a phase-only analysis with the goal to obtain a continuous clock solution which is independent of the GPS codes. In this paper, the analysis strategy used in Atomium is described and the clock solutions obtained through the phase-only approach are compared to the results from the PPP mode. It is shown that the phase-only solution improves the stability of the time link for averaging times smaller than 7 days and that the phase-only solution is very sensitive to the station coordinates used. The method is, however, shown to perform better than the IGS clock solution in case of changes in the GPS receiver hardware delays which affects the code measurements.